Discount Calculator
From original price and discount, get the amount paid and savings, or reverse the discount rate from original and current price.
Discounts: percent off, the 'zhe' scale, stacking rules and threshold order
Percent off is the main line; "zhe" is the Chinese term
In English-speaking retail the usual phrase is "X% off" — the percent you save. The Chinese interface of this tool instead uses a term written "zhe", where "X zhe" means you pay X/10 of the price. So 8 zhe = pay 80% = 20% off; 7 zhe = pay 70% = 30% off. The conversion runs: zhe = 10 × (1 − off fraction). "30% off" therefore equals 7 zhe. The two scales run in opposite directions — a smaller zhe number means a bigger discount, which is the part that trips people up.
| Term | Share paid | Saved |
|---|---|---|
| 9 zhe | 90% | 10% |
| 8 zhe | 80% | 20% |
| 8.5 zhe | 85% | 15% |
| 7 zhe | 70% | 30% |
The easiest mistake: "20% off" is not "pay 20%". And because the tool's field takes the zhe number, 8 means 20% off (pay 80%), not 8% off. Amount paid = original × zhe / 10.
Stacking discounts always multiplies
| Stack | Wrong | Right | Result (original 100) |
|---|---|---|---|
| 8 zhe then 9 zhe | 7 zhe → 70 | 0.8 × 0.9 = 0.72 | 72 |
| 8 zhe then 8 zhe | 6 zhe → 60 | 0.8 × 0.8 = 0.64 | 64 |
| discount + 10% coupon | add | multiply | apply each once |
When two discounts stack, the real discount is always smaller than their sum. The second row is the clearest trap: two 20%-off events feel like 40% off, but are actually 36% off (0.8 × 0.8 = 0.64).
Discount-then-threshold vs threshold-then-discount differ
The place shoppers lose money most often. With original 300, "spend 200 get 50 off", and an extra 20% off:
| Order | Calculation | Paid |
|---|---|---|
| Discount first, then threshold on reduced price | 300 × 0.8 = 240 → minus 50 | 190 |
| Threshold first, then discount | 300 − 50 = 250 → × 0.8 | 200 |
Same promotion, 10 apart depending on order. A third, sneakier case is whether the threshold checks the post-discount price: some rules require "still meets the threshold after discount", so 240 qualifies, but a deeper discount dropping to 190 would not. The rule is set by the merchant, with no universal standard. The only reliable check is the settlement note on the activity page or the final cart amount — do not estimate it yourself. This tool computes a single-layer discount and reverses a discount rate; it does not model complex stacked promotions.
Reversing the discount rate
Given original and current price you can reverse the discount:
zhe = current / original × 10, saved fraction = (1 − current / original) × 100%
Useful for checking whether a merchant's claimed discount is real, comparing which pack size is actually cheaper (unit price is the comparable basis), and judging what "second item half price" equals.
On that last point: "second item half price" equals an overall 7.5 zhe (two items cost 1.5 of one, 1.5 / 2 = 0.75), not 5 zhe. "Buy two get one free" equals 6.67 zhe (2 / 3), "buy three get one free" equals 7.5 zhe (3 / 4). The more free items, the smaller the real discount — "buy three get one free" is worse than "second item half price".
Hidden factors beyond the discount
- When tax is computed — before or after discount varies by setting.
- Whether shipping participates — common rule is the discount applies to goods only, shipping separate.
- Whether the original price was inflated — "raise then cut" is common; judge real savings against the historical price, not the listed original. A price-tracking tool or a platform's price history shows the truth.
- Pricing psychology. 99 and 100 differ by 1, but 99 at 10% off is 89.1 and 100 at 10% off is 90; after rounding both may show 89 or 90 and the real difference vanishes. Watch rounding on small savings.
How the tool works
Enter original price and zhe for the amount paid and saved; or enter original and current price to reverse the discount (zhe and percent). Both directions can run together and both show. All math is local, with no upload.
FAQ
What goes in "Discount"?
Enter the "zhe" number, e.g. 8 for 20% off (80%). Amount paid = original × discount / 10.
How to reverse the discount rate?
Enter both original and current price; the tool shows the discount factor (zhe and %) and the amount saved.